PSR-1A Seismic Instrusion Detector

Vietnam-Era PSR-1A Seismic Intrusion Detector Set, including ground rod, and 4 geophones. The geophones, or strings thereof, are deployed up to 1 mile away from the control box, and connected via field telephone wire (WD-1(A) or equivalent) The control unit can monitor 4 strings of sensors simultaneously. The sensors will detect footsteps within a 100' radius, depending on soil type and conditions.
The controller runs on 6ea. D-Cells. As this unit was designed for older carbon-zinc cells, use of modern alkaline cells requires a layer of electrical tape, or other insulating material around the body of the battery, to prevent shorting against the retaining clips.
The operating controls are simple, and easy to understand, and with a little practice, one can classify personnel, vehicles, and animal traffic. When the meter switch in the LINE position, The meter indicates line condition when the test switch for that sensor string is activated. Meter deflection to the Left Side indicates a short in the line, a reading in the Center indicates a good line, and a deflection to the Right indicates an open line. When the meter switch in in the BATTERY position, a deflection to the Right indicates a GOOD battery. The meter is disabled in the OFF position to conserve battery life.
Connection of a high-impedance headset to the front panel terminals deactivates the internal speaker.